Evolution is a fundamental concept in biology that describes the gradual change in living organisms over time. It encompasses the idea that species arise, adapt, and branch out through a process driven by various mechanisms. Charles Darwin's theory of evolution by natural selection is widely accepted and forms the basis for modern evolutionary biology. It posits that advantageous traits are more likely to be preserved in a population, resulting in the survival and reproduction of individuals better adapted to their environment. Evolution can occur through small-scale changes within a species (microevolution) and larger-scale transformations leading to the emergence of new species (macroevolution).